New Editor

A new method of gene editing in human cells has been developed

Tatiana Matveeva, "Scientific Russia"

Over the past decade, the CRISPR genome editing system has revolutionized molecular biology by allowing scientists to modify genes inside living cells for research or medical purposes. Now scientists have improved an additional system for more efficient gene editing using retron molecules, the press service of the Gladstone Institute (USA) reports.

Retrons are a DNA sequence found in the genome of many bacterial species that encodes reverse transcriptase, and a unique single-stranded DNA/RNA hybrid called multi-stranded single-stranded DNA. The results of the study are published in the journal Nature Chemical Biology (Lopez et al., Precise genome editing across kingdoms of life using retron-derived DNA).

The CRISPR system works as follows: a section of DNA is cut out of the cell genome, and it is replaced with "template" DNA – new genetic material. "Template" DNA is usually produced in the laboratory, and then injected into cells from the outside. The protein that cuts the cell genome – Cas9 – is delivered separately. Neither Cas9 nor the DNA patch penetrates into every cell, which limits the effectiveness of CRISPR gene editing.

Retrons act as DNA factories, producing a large number of copies of template DNA inside cells. In addition, the retrons can be delivered along with the rest of the CRISPR components so that cells simultaneously receive all the material needed for gene editing — genetic codes for template DNA, Cas9 and molecules that help researchers track the changes made.

This means that instead of several elements, it is enough to enter only one element into each cell, the authors note. And this greatly simplifies the process of gene editing. 

Retrons, like CRISPR– are initially protective tools of bacteria. Bacteria use them to alter DNA in response to infections. In this study, scientists have developed hundreds of new variants of E. coli retronas. They checked each new option and found a number of changes. Some variants could produce eight to ten times more "template" DNA.

The researchers then tested the newly reconstructed retron system on baker's yeast (Saccharomyces cerevisiae fungus) and cultured human cells and found that the optimized system works in all cases.

So, scientists can now fine-tune how much "template" DNA the retrons should produce. They were also able to show that the more DNA the retrons produce, the more efficient the genome editing will be. These cells can be used to edit genes in various types of cells, from fungal cells to human cells.

Portal "Eternal youth" http://vechnayamolodost.ru